1. Field of the Invention
This invention relates to new and useful improvements in machines for working sheet metal, particularly for closing sheet metal joints of the type commonly known as the "Pittsburgh Lock", and more particularly to an automatic machine for continuous application of a hammering force to the edge portion of a joint to be formed to fold such edge into a closed joint.
2. Description of the Prior Art
In the past, the formation of sheet metal joints in duct work has been done by hand or by complicated machinery for rolling and forming the desired seams or joints.
Lindgren U.S. Pat. No. 1,612,519 discloses an automatic seaming machine for sheet metal having rotary cams for folding and bending seams.
Brown U.S. Pat. No. 1,381,062 discloses a rotary brake for forming seams in sheet metal products.
McCann U.S. Pat. No. 1,625,269 discloses an automatic seaming device for cylindrical objects such as cans.
Flagler U.S. Pat. No. 2,950,697 discloses a rotary device for forming seams in sheet metal.
Tribe U.S. Pat. No. 3,130,770 discloses a rotary device for bending or folding the edges of sheet metal panels to form seams therein.
Gibson U.S. Pat. No. 2,810,420 discloses a rotary hammer for closing sheet metal joints of the type known as the "Pittsburgh Lock".
Kemp U.S. Pat. No. 3,638,596 discloses another type of rotary hammer for closing sheet metal joints of the type known as the "Pittsburgh Lock".